#include <reg52.h>

void delay1ms(unsigned int i)
{
	unsigned char j;
	while(i--)
		for( j=0;j<115;j++);
}
void main()
{
	EA=1;
	EX0=1;
	IT0=1;
	while(1)
	{P1=0x00;}
}
void it() interrupt 0
{
	unsigned char i;
	EX0=0;
	for(i=1;i<=3;i++)
{
	P1=0x0f;
	delay1ms(100);
	P1=0xf0;
	delay1ms(100);
}
EX0=1;
}
